1. Chapter 13
Section 1

2. Introduction
For centuries the nature of light was disputed. In the 17th century, Isaac Newton proposed “corpuscular theory” stating that light is composed of particles. Other scientists, like Robert Hooke and Christian Huygens, believed light to be a wave. Today we know that light behaves as both a wave and as a particle. Light undergoes interference and diffraction, as all waves do, but whenever light is emitted, it is always done so in discreet packets called photons. These photons carry momentum, but not mass.
Robert Hooke
Christian Huygens
Isaac Newton

3. Light is a visible electromagnetic wave.
It is best classified as a transverse wave though no matter is actually moving, unlike a water wave or a string being moved.
Because it is an electromagnetic wave it requires no medium.
What does this mean for other electromagnetic waves?

4. Light and Matter
Objects can absorb light, reflect light, and transmit light.
Opaque—Light can not pass through all it can do is absorb and reflect light
Transparent—Light can pass through it almost completely
Translucent—Light can pass through but is scattered.

5. Reflection
A Reflection occurs when light strikes an object and then bounces off
There are two main types of reflection in light, regular and diffuse.
Regular= mirror
Diffuse= color but no image
The rougher the surface the more diffuse the reflection will be

6. Refraction
Refraction is what happens when light speeds up or slows down as it changes mediums.
The index of refraction indicates how much the speed of light will change based on the material an object is made of. Ex. Water has a large index of refraction than air.

7. Prisms and Rainbows
A prism can refract white light into 7 different wave lengths of visible energy.
This is more commonly called a rainbow.
The 7 wave lengths correspond to the 7 colors of a rainbow: Red, Orange, Yellow, Green, Blue, Indigo, and Violet.
Water is an example of a prism.

8. Mirages
A mirage is an image of a distant object produced by the refraction of light though air layers of different densities.
They are a result of the air at “ground” level is much warmer or cooler than the air above it.
Light travels at different speeds depending on density. Temperature affects density, the colder the air the more dense it is. This is how light refracts and creates a mirage.

9. Content Check
What is the difference between regular and diffuse reflections?
How does refraction occur?
What is light?
What is a particle of light called?
What is a mirage?